Method of and means for controlling electrical and magnetic pulsations



M. L. sEvERY 1,914,173

METHOD OF AND MEANS FOR CONTROLLING ELECTRICAL AND MAGNETIC PULSATIONS June 13, 1933.

Filed June 19, 1931 Gttornegs Paremed June 13, 1933 UNITED STATES ,PATENT OFFICE'.

MELVIN SEVERY, OF LOS ANGELES, CALIFORNIA, ASSIGNOR TO THE VOCALSEVRO y COMPANY, F LOS ANGELES, CALIFORNIA, A CORPORATION OF DELAWARE :METHOD OF AND MEANS FOR CONTROLLTNG ELECTRICAL AND MAGNETIC PULSATIONS Application led June 19,

This invention relatesmore particularly to the conversion of direct currents of electricity into rhythmical pulsations, and one'of its chief uses is in that type of musical instruments where eleotromagnets are -employed to generate the tone-producing impulses.

Other important objects of the invention are to increase the efficiency of operation t0 an extent which makes possible a decrease in the operating voltage with the same magnet windings; more perfect operation; and greater durability of the current-pulsating mechanism. Y

Another important object of the invention is the suppression, to a negligible` point, of the arcing which ordinarily occurs at the Y 'brushes of current-pulsating mechanisms.

In U. S. Patent No. 1,104,939, entitled Electric musical instrument, issued-to M. L. Severy-and G. B. Sinclair and dated July 28, 1914, a commutating mechanism is shown and claimed, with conducting brushtraversed sections shorter than the non-con- 'I ducting sections by at least the lap of the brush. As therel stated, the purpose of such construction .was that current should never be in the associated magnet for'more than half of the time; that is to say, that during operation, the live instants of the magnet should never eX'ceed the dead instants.

When considering a magnets attraction of its armature in rhythm with the pitch of some note of the musical scale, it is inevitable that the periods of approach toand recession from the core should be thought equal in time, and it is most natural that it should be considered that this dictated, where `a commutator is used, conducting sections which should at least be' as small as the non-conducting sections, to the end that the live instants of the associated magnets should never exceed in duration the dead instants thereof. This conclusion, natural as it seems, I have discovered to be most erroneous, as will appear as this specification proceeds.

In the drawing:

Fig. 1 is a diagrammatic View showing, partly in elevation and partly in section, a

1931. Serial No. 545,611.

commutating mechanism embodying my ini' vention and aspeaking unit actuated thereby, the driving means for the commutator being omitted;

Fig. 2 is a view of said speaking unit,

taken at right angles to that shown in Fig. 1; Fig. 3 shows an enlarged segmental portion of a commutator ring,'disk or member having a different number of conducting and non-conducting sections from that shown in Fig. 1.

In Fig. 1 the numeral 1 indicates a sec-'l A brush 4' contacts with the periphery of the i commutator section, another brush 5 bearing upon the central shaft 6, or being otherwise constantly in electrical communication with commutator section 1. 7 indicates a source of electricity and 8 a pole thereof, in this case a positive pole. A contacting member 9 is carried by a key l0 and adapted to coact with the pole 8 upon the pressure of a key 10 of the manual. This showing is purely diagrammatic, `all unnecessary details being omitted; A wire 11 joined to contact 9 at one end leads to the magnet 17, from which another wire 16 connects with wire 16a leading to brush 4 through which and the commutator section 1 and brush 5, the circuit is completed to the negative pole of the source of current 7. A condenser 12 and a resistance 13, preferably non-inductive, in shunt therewith, are introduced for the purpose of suppressing the arcs when brush 4 leaves a conducting area of commutator section .1. This condenser 12 may be off-ordinary form; it may be of the liquid or dry electrolytic type; or it may be some other form of capacitator, and may be employed with or without a resistance in shunt or otherwise. Moreover, the condensermay be, and in some cases I have found it well that it should be, across the magnet instead of across the break. I have indicated this location in dotted line at 15 with 14 as a resistance.

As seen in Figs. 1 and 2, the magnet 17 by nuts 19, 2O said core opposing anarmature 38 threaded into the ribbed plunger- -type diaphragm 23 held flexibly at the end of resonator 21 by the membrane 23a of rubber-cloth, leather, or other suitable material. This membrane is secured to resonator 21 at its edges by a metallic ring'A or annulus 39, here shown of trough-likeform in cross section, and fastened to resonator 21 by screws. The membrane 23a is secured to the edges of. the plunger-diaphragm 23 by a'circular clamping ring or band 25 secured by screws to the projecting edge 24 of said diaphragm. Diaphragm 23 is thus left free to reciprocate vertically under the action of magnet 17 upon the flexible bar 26 to which said diaphragm is fastened and by which it is carried. Pins 27 pass freely througlh flexible bar 26 and are firmly seated in t e adjustable members 28, so that when the adjusting screws 32, the inner ends of which bear against the fixed frame or magnet-housing 35, are turned in proper direction to move the upper ends of supporting members 28 outward, bar 26 will be put under longitudinal stress or tension, thus adjusting it, at least roughly, to its load and periodicity. Any Obliquity or deviation from verticalv position of the supporting members 28 incident to such adjustment by screws 32, will be corrected by very slightly backing off the nuts 30 carried by the outer ends f the fixed rods 29, which rods carry the supporting members 28, and are themselves carried by the fixed frame 35.

This construction makes it possible to keep a straight draft upon flexible bar 26 during its various adjustments. Clampin bolts and nuts 40, 41 limit the free lengt of bar 26 and secure it against rattling. The bar-adjustin members 28 are arranged to afford two a justments, one at either end, so

/that their pull may be ke t sensibly normal to bar 26 upon which t ey act. The adjustable magnet-housing 35 is formed or furnished with bracket members 37, perorated to receive rods 31, each threaded at its upper end and screwed into tapped lugs 22 projecting inwardly from plates 22 secured by screws or other fastenings to the base of resonator 21. To prevent the loosening of the rods 31, set screws may be employed Aas shown in Fig. 1. The lower ends of rods 31 pass through the perforated horizontal portion of the bracket members 37, as best seen in Fig. 2, said rodsbeing provided at their lower threaded ends with nuts 33 placed one above and another below each of said plates. By proper adjustment of said nuts 33, the magnet housin may be raised or lowered as desired, an

securely held in fixed relation to the diaphragm 23' and connected parts. The plates 22 may advantageously be formed with ribs or flanges 34 to facilitate their positioning on v `amperes of current if there were no interruption or pulsation therein. I have found` however, that when the current is interrupted, say, thirty-two times a second with the dead instants and the live instants of the magnet equal in duration, the current will d rop to a small fraction of the former amount, for example, to four-tenths of an ampere. Under these conditions the speaking unit will be actuated rhythmically so far as the energizing magnet is concerned, and the same would be true if the dead instants of the magnet were of twice the duration of the live instants. Inv the latter case,

however, there would be a very great decrease in efiiciency. It has been the common thought that if the live instants of a magnet exceeded in time the dead instants thereof, there would be a hold-over. or a tendency to retain the magnet near the core when it ought to be freel receding therefrom, thus decreasing the e ciency of the magnet and,

asit were, stifling the resultingtone. I have found this seemingly natural conclusion to be entirely erroneous, and many and most carefully 'conducted tests have clearlydemonstrated that not only may the live instants of the magnet be increased in time beyond the time of the' dead instants with- Yout hurting the efficiency or marring the Iwhen in its'housing, as shown, and another way when operated outside of said housing. In the housing it is provided with a most excellent return circuit, the housing being usually of cast iron and bar 26 being of steel, with the armature or part 38 also of magnetic metal. This would be expected to give a stronger pull than when the return loo circuit is through a long air-gap. It has been ascertained, however, that this condition of affairs decreases somewhat the current consumption ofthe magnet, and that it has a pronounced effect uponthe arc at the commutator, which, tested Without a condenser, it seems to cut down in roportion to the nearness of the approach oP the armature tothe core. If the armature be permitted to remain in contact with the core, the arc is decreased, judging'by its appearance, from 80 to 90 per cent, and at practical working distance the decrease in the arc is very noticeable over what it is with the same magnet without housing and metallic return circuit throughout all but a triiing portion of its distance from pole to pole. The suppression of the arcs being the largest factor in the eiiicient life of commutators and brushes, this discovery and method of applying it are of great importance, since when it is used there is less left for condensers, electrolytic cells, capacitators, or the like to accomplish in rendering the arcs negligible.

Furthermore, the method herein set forth produces a sound-wave of better l-form as well as of greater power and efliciency. In a musical instrument, say of seven oct'aves, it is customary to cover a vibrational range, of from 32 to nearly 4,000 per second and, since it is desirable to use commutators of reasonably small diameter for reasons. of' cost and compactness, it will readily be seen that the commutating members ,serving the higher notes must of necessity have more and therefore much smaller teeth than those serving the lower notes. Moreover, the amount of currentJr taken by a magnet varies greatly with the period of its pulsations, being less the more rapid these are. By reason of these facts I wish it distinctly understood that I do not confine myself to any one ratio of dead and live instants in the' magnets, as the ratio of those magnets serving notes of high pitch will preferably be different from that of those magnets serving notes of low pitch. 1

I have found that a live instant of 80% anda dead instant of 20% is well'suited to a very low note, but the smallness of the teeth of commutator members serving very high pitches together with the lap of brushes of suiiicient-thickness for stability/renders it advisable if not imperative with commutators of moderate diameter serving such high notes, to decrease this 80% live instant to some extent,y though preferably keeping it as large as conditions will permit. In cases Where the size of commutators may be,

'increased suiiiciently to permit it,`this 80% live instant is preferably employedl even with the very highest note, much better results being thus secured. However, in an instrument built to serve the needs of the general` public inthe matter not only of results but of price and size, it is preferred, ordinarily, to vary the live instants as the lpitch ascends, though not necessarily with every note of the scale but rather by groups or sections.

It isV obvious that a current could be pulsated without at'any time entirely stopping Athe flow thereof, and that a current of this character when energizing a magnet would result, not in live and dead instants of said magnet, but in instants more alive and less alive, for which reason it is expressly to be understood that wherever in this specification or its associated claimsl the terms live and dead7 instants are used, they are speciically-meant to include instants which are more alive and those which are less alive though not necessarily entirely dead.

It is also to be understood that wherever in this specification or its associated claims, pulsations in the current are referred to. this has been done with the express intention y v of covering rhythmical current changes including actual make and break, aswell as rhythmical variations in a current some of i which is continuously flowing.

In order to avoid complicating the showing of this application, and for the further reason that it is an art so well known, .all

unnecessary details, including the driving v means for the commutating mechanism, have been omitted, the drawing being largely diagrammatic. It is vto be understood, of

course, that the commutators or their equivalents are to be driven by carefully timed speed mechanism, suitable types of which are shown in other -patents granted to me and in pending applications filed in my 1 name. y

Furthermore, no attempt has-been' made to show the exact construction of the commutating mechanism, its variously sized teeth, and the like. It should be stated, however, that a conducting substance is commonly mixed with the cement or other material used to fill the non-conducting areas of the commutator, thus lowering their resistance. It is" tobe understood, therefore, that when conducting and non-conducting areas of the commutator are referred to, this phraseology includes'also areas of relatively low and high resistance, respectively, since Y there are distinct advantages in lowering the resistance of the non-conducting areas by the admixture of the conducting substance as stated, and this constructionis ordinarily employed.

What is claimed is l. The herein-described method of increasing the eiliciency of a rapidly responsive electromagnet, which consists inv creating rhythmical current increments and de-v erements in the electricity energizing said electromagnet, the said increments being of substantially longer duration than the alternate decrements.

2. The herein-described method of increasing the eiiciency of rhythmical electrical pulsations delivered to an electromagnet, which consists in making the live instants of the magnet, Whenin operation, of substantially longer duration than the dead instants thereof.

3. The herein-described method of producing pulsations in an electric current, Which consists in delivering the current to a commutating member co-acting with a brush, said brush and the low-resistance portions of said member traversed thereby being so proportioned that, in operation, the co-acting low-resistance surfaces thereof will be in electrical contact substantially more than half of thetime.

4. The herein-described method of increasing the eiiciency of a rapidly responsive electromagnet, which consists in' creating rhythmical current increments and decrements4 in the electricity energizing said electromagnet, through the agency of alternately operative high and low resistance commutator areas associated with a c0-act ing brush, the low-resistance areas being circumferentially longer than the highk resistance areas.

5. The herein-described method of increasing the eliiciency of sets of rhythmical electrical pulsations, the sets being of different periodicities and delivered to electromagnets, one for each said set, said method consisting in making the live instants of the magnets, when in operation, of substantially longer duration than the dead instants thereof, and in varying the ratio of live to dead instants in magnets associatedywith some of the different periodicities.

6. The herein-described method of pro- -ducing pulsations of various frequencies in an electric current, which consists in delivering the current to make-and-break mechanism having a plurality of sections each thereof provided with a co-acting brush, each of said brushes and its associated conducting portions of the mechanism traversed thereby being so proportioned that, in operation, the co-acting conducting surfaces thereof Will be in electrical contact sub'- stantially more than half of the time, the ratio of the time of contact to non-contact vary-ingin dilferent parts of the mechanism producing different periodicities of 'pulsations.

7. The herein-described method of `altering the Wave-form of the magnetic flux of an electromagnet energized by pulsating current, which consists in making the live instants of the electromagnet of substantially longer duration than its dead instants.

8. The methodl of producing different magnetic waveforms/and increasing the efficiency of the magnetic fluxes of electromagnets energized by pulsating electric currents having the periodicities of the notes of a musicall scale, lfor use in connection with associated mechanism to produce sounds of said periodicities of vibration, said method consisting in rendering the live instants of the electromagnets of substantially longer duration than their dead instants, and in producing in some of the electro-magnets time-ratios of live to dead instants different from those subsisting in other of said electromagnets. l

9. In an electrical current-pulsating mechanism, means for minimizing arcing and prolonging the periods of energization of said mechanism, comprising a source of direct current and suitable connections, commutating members and associated brushes adapted, when relative motion is produced between them, to cause alternate increments and decrements in the flow of the commutated current, theincrements occupying substantially more time than the decrements.

' '10. In an electrical current-pulsating mechanism, means for minimizing arcing and prolonging the periods of energization of sa1d mec anlsm, comprising commutating members having circumferentially distributed areas of alternately high and low resistance material traversed by a brush, the

Ycontact of said brush with the areas of low -reslstance being of substantially longer ldu ration than the contact with those of high resistance.

11. In an electrical current-pulsating mechanism, means for minimizing arcing and prolonging the periods of energization of said mechanism, comprising commutating members havingv circumferentially distributed areas of alternately high and low resistance material traversed by a brush, the low resistance areas being longer circumferentially than the high resistance areas.

l2. In an electric musical instrument, the combination of a series of resonators each serving to furnish a note of the musical scale; a plunger-diaphragm associated with each resonator and provided with an armature; a magnet supported i'n proximity to each armature; current-pulsating members each bearing upon its circumference succes'- sive areas of alternate high and low resistance material, the low resistance areas being substantially longer in the direction of travel than the high resistance areas; a brush associated and contacting with each of said current-pulsating members; a source of electric current; and electrical connections between the source of current, the several current-pulsating members, and. their associated magnets. A

13. The herein-described method of increasing the eiiiciency and improving the action of a rapidly responsive electromag- ALIIS net, which consists in creating rhythmical current increments and decrements in the electricity energizing said electromagnet,

through the agency of electrically conductl ing commutator areas of high and low resistance associated With a co-acting brush, the low resistance areas when traversed by said brush in operation, furnishing current increments of longer duration than the a1- ternate current decrements.

14. In an electrical current-pulsating mechanism, circumferentially distributed areas of high and low electrical conductivity traversed by a brush, the current increments produced b the passage of the brush over the areas o high conductivity being of substantially longer duration than the current decrements produced by the passage of the brush over the areas of low conductivity, the last-named areas being formed of a Inaterial containing or treated with, an elecf trically conducting-substance.

15. In an electrical current-pulsating mechanism, circumferentially distributed areas of high and low electrical conductivity traversed by a brush, the current increments produced by the passage of the brush over the areas of high conductivity being of substantially longer duration than the current decrements produced by the passage ofthe brush over the areas of low conductivity, the last-named areas being formed of av material containing, or treated with, a frictiondiminishing lubricant.

In testimony whereof Il have igned my nameto this specification.

' MELV'IN L. SEVERY. 

